Computing sight



May Z4, 1949.

Patented May 24, 1949 COMPUTING SIGHT Richard M. Elliott, Beverly, Mass., assigner to United Shoe Machinery Corporation, Flemingf ton, N. J., a corporation of New Jersey Application February 11, 1946, Serial No. 646,869

3 Claims.

This invention relates to gun sights and more particularly to a computing sight adapted for use with an antiaircraft gun.

Owing to the relatively high speed of a target presented by an attacking aircraft, the sights of an antiaircraft gun should be arranged to cause the line of fire to lead the line of sight to the target. One Well-known sight meets this problem, as against a target in level iiight, by the provision of means for automatically changing the horizontal lead angle between the gun and the sight as the gun is trained, this means being subject to manual adjustment in accordance with the estimated horizontal speed of the target. If the estimate is correct, the gun is kept on the target throughout an extended range of training movement by so laying the gun as to keep the target on the line of sight.

However, attacking aircraft, when within the most effective range of an antiaircraft gun, are often in a dive rather than in level flight. The necessity for leading such a target vertically, as wel1 as horizontally, is manifest. When such a target is tracked by reference to the path of tracer shells, the target moves off the axis of a sight of the type referred to above since it is not adapted to compensate for the rapid change in elevation of the target. Accordingly, in laying the gun -by the use of the sight, it is necessary to maintain the target off the axis of the sight to an extent lbased upon experience, even after the best possible estimate of horizontal target speed and the corresponding adjustment of the sight have been made.

In view of the foregoing, it is an object of the present invention to provide an improved gun sight, the use of which will increase the effectiveness of a gun against a diving target and will entail a minimum of off-center tracking of the target in the sight.

To this end, the invention provides a gun sight, which, as herein illustrated, includes provision for manually establishing a proper lead in .both azimuth and elevation between the line of fire and the line of sight for estimated horizontal and vertical `components of the targets velocity, and means for maintaining this lead or the proper variation thereof for producing a succession of hits when the target is kept on, or in a xed relation to, the axis of the sight.

These and other features of the invention are disclosed in the following description and the accompanying drawings and are pointed out in the claims.

In the drawings,

Fig. 1 is a view in perspective showing schematically a computing sight constructed in accordance with the present invention, and illustrating diagrammatically the adjustment and operation of the sight.

The illustrated sight comprises a pair of brackets I0, I 2 which are fixed to a sight support I4, the latter being rigidly connected to the gun turret (not shown). The turret is mounted for rotation in elevation on a carriage which is mounted for rotation in azimuth, this arrangement being characteristic of many mounts and particularly the so-called Maxson mount, in connection with which the present gun sight was designed. In the operation of this mount, the operator of the gun is seated in the turret and manually controls power-operated mechanism for moving the carriage in train, and for moving the turret in elevation relatively to the carriage so as to lay the gun on the target.

Since the details of construction of the mount are well known and have no direct .bearing on the present invention, they have been omitted from the drawings; but such movements of the mount as are utilized in connection with the operation of the present gun sight will be more fully described below.

Between the lower rear arms of the brackets I Il, I2 is rotatably mounted a shaft I6 which carries a yoke I8. The shaft and yoke are thus arranged to rotate about an axis which is perpendicular to the 'bore of the gun. The illustrated sight comprises a reticle sighting element 20 which is fixed to and actuated by a sight bar comprising a tube 22 and a rod 24 which telescopes within the tube. The tube 22 is arranged to rotate within the yoke I8 around a pivot 26, the axis of which is perpendicular to that of the shaft I 6. The sighting element 20 is thus mounted for universal movement about a point (at G) which is xed relatively to the gun. The forward end of the rod 24 carries a ball socket 28 which is positioned adjustably in space by a slide 30 so as to establish a lead between the gun and the line of sight.

The slide 30 is adjustable in translation, for a purpose to be explained hereinafter, along a rod 32 which is carried by a yoke 34. The yoke 34 is mounted on a shaft 36 to rotate in a support 38 about an axis which intersects (at L) a line parallel to the bore of the gunA and which also passes through the pivot 26 at G. As will also be described later, the yoke 34 is provided with a series of graduations to assist in adjusting the 3 slide 3D in accordance with the estimated horizontal speed of the target.

The support 38 is mounted for adjustment vertically on a pair of rods 40, 42 which at their lower ends are pivotally mounted on the forward arms of the brackets I and I2 respectively. The vertical adjustment of the support 38 is effected manually yby turning a knob 44 the rim of which is provided with a series of graduations corresponding to vertical components of the targets velocity. The knob is fixed to a shaft 46 which is rotatably mounted in uprights 48-48 formed integral with the support 38 and carries a pair of gears 50-50 which mesh with racks 52-52 cut into the rods 40, 42. It will now be apparent that, by turning the knob 44, the support 38, the yoke 34 and hence the ball socket 28 will be moved to establish a vertical lead of the gun with re spect to the line of sight.

As will appear more fully hereinafter, the principle of operation of the illustrated sight requires that the yoke 34 be positioned and maintained parallel to the horizontal component of the targets velocity. A requisite to maintaining this relation consists in also maintaining the axis of the shaft 36 vertical at all times regardless of any movements of the turret in elevation. In order thus to maintain the orientation of the yoke 34 co-nstant in space, regardless of the movements of the gun in azimuth and elevation, equal and opposite movements must be imparted to the yoke 34.

Referring first to the provision for maintaining the shaft 36 in a vertical position, a worm gear 54 is pinned to a shaft 56 to which the rod 40 is also pinned. The shaft 56 is rotatably mounted in the forward arm of the bracket IU. The gear 54 is driven by a worm 58 fixed to one end of a flexible shaft 60, the worm being adapted to be rotatably mounted in a housing (not shown) fixed to the bracket Il). The other end of the shaft 60 carries a pinion which is adapted to be mounted for rotation on the turret and in mesh with the usual elevating ring-gear. This gearing is so designed that upon any movement of the turret in elevation, an equal and opposite movement is imparted to the support 38, and hence to the shaft 36 and yoke 34. Thus, when once the sight is assembled with the shaft 36 disposed vertically,

the shaft will remain in this position regardless of movements of the turret in elevation.

The azimuth control of the yoke 34 is effected by similar means comprising a worm gear 62 which is fixed to the shaft 36 and a worm 64 which is driven from the training ring-gear of the mount. The worm 64 is operated by a flexible shaft inside a cable 66 which is ,connected to a differential 68 of usual construction. The drive is -completed by another flexible shaft housed in a flexible cable which extends from the differential to a position on the carriage adjacent to the usual training ring-gear. The differential 68 comprises a control crank 12 which, when turned, will cause a movement of the worm 64 without interfering with the drive to the differential from the training ring-gear. Accordingly, by turning the crank 12, the yoke 34 may be positioned in parallelism with the horizontal components of the targets velocity. Thereafter, any movement of the gun carriage in azimuth will impart through the connections just described an equal and opposite movement to the yoke in azimuth relatively to the carriage, whereby the orientation of the yoke 34 in space is maintained constant.

In order to assist the operator in adjusting the yoke 34 in parallelism with the targets course, the illustrated sight is provided with an indicator 'f4 which is always orientated like the yoke 34 and is located in an unobstructed and convenient line of sight to the target. The indicator is carried at the lower end of a, shaft 16 which is rotatably mounted in the support 38. The shaft 16 is operated in synchronism with the shaft 36 by a gear train comprising a gear 18 fixed to the shaft 16, an idler gear and a gear 82 which is fixed to the shaft 36. The above-mentioned gear train, as well as the worm gear 62, and the worm 64, are adapted to be mounted in a housing (which has been eliminated to clarify the drawings), associated with the support 38.

Considering now the principles and operation of the illustrated sight, assume the target, an aircraft, to be on a diving course at the point To, having a velocity V, and to be at a predicted position Tp after a certain interval of time tp. The course lies in a vertical plane DTnTp which is inclined at angle C with a vertical plane AToB, the latter plane being perpendicular to the axis of the bore of the gun.

The targets velocity V may be considered as having a horizontal component Viv and a vertical component Vv. The indicator 14 and hence the yoke 34 are now alined with Vn by operating the crank 12, and the slide 30 is adjusted along the yoke into a position corresponding to Vn as estimated by the operator.

With this adjustment of the sight, when the line of sight through the sighting element 20` is directed at the target at To, the gun will lead the line of sight horizontally by the angle Ln, and a shell fired from the gun would intercept the plane of the course at point S directly above Tp if no correction were made for the vertical component Vv. To make the correction last referred to, the knob 44 is turned to raise the yoke 34 through a distance corresponding to Vv as estimated by the operator. The gun will now lead the line of sight vertically by the angle Lv. Now the line of fire is depressed relatively to the line of sight with the final result that a shell red from the gun and the target will meet on collision courses at Tp if the operators estimates of Vh and Vv are correct.

The speed scales on the yoke 34 and knob 44 corresponding to estimated values of Vn and Vv are determined from the following:

When the yoke 34 is adjusted into parallelism with the plane TuTpR, the plane LMN also is parallel to the plane ToTpR, and the line LM is parallel to the line TpR. From similar triangles.

(l) LM/ LG=TpR TpG where LM is the displacement of the slide 30 from the axis of the shaft 36 and LG is the xed distance between the shaft 36 and pivot 26. LG is established arbitrarily on the basis of the desired size of the sight, 4- inches being a suitable value. Since TpR=V1L multiplied by the predicted time tp in which the target goes from To to Tp and, since TpG=the distance from the gun to the target at the end of time tp, Equation 1 may be rewritten as follows:

(2) LM/lzVMtp/TpG) Now TDG/'tp is equivalent to the average shell velocity over the distance TpG for the usual range of firing to which a xed value can be assigned for a given type of ammunition. Assuming that 740 yds/sec. is such a value, Equation 2 may be rewritten as follows:

From Equation 3, it is apparent that, for an estimated Vn of 185 yds/sec. (about 380 mi./hr.) LM would be one inch.

In a similar manner, a series oi values for LM in terms of Vh can be determined from which it is possible to graduate the yoke 34 directly in terms of target speed in miles per hour.

In the same manner, graduatons for the knob Gil can be determined.

Errors in the estimates of Vn and Vv will show up as a slight misalinement of the target and the line of sight when the gun is laid by tracer tracking. The shortness of time when the target is in range does not permit successive readjustments of the slide 30 and knob 44. However, the nal correction employing slightly off-center tracking in the reticle sighting element is small when the operator of the gun has a good knowledge of aircraft types and their probable speeds.

I-Iaving described my invention, what I claim is:

1. In a gun sight for use with a gun mounted to swing in azimuth and elevation, a sighting element, a sight bar carrying said element and mounted for universal movement about a pivot point which is xed relatively to the gun, sight operating means comprising a support mounted for rotation about and translation along an axis which intersects a line parallel to the gun and passes through said xed point, means nperated insresnonsatnaingrent oithszsgrrinazimuth to impart an equal andpposite rotation to said support about said axis thereby to maintain constant the orientation of said support in space, means operated in response to a movement of the gun in elevation to impart an equal and opposite angular movement to said support whereby said axis is constantly maintained in a vertical position, and means for causing the gun to lead the line of sight in elevation and azimuth, said means comprising operator-controlled connections for adjusting said support in translation in the direction of said axis and a slide to which said sight bar is pivotally connected, said slide being adj utable in translation on said support perpendicularly to said axis.

2. Ina gun sight for use with and mounted on a gun mounted to swing in azimuth and elevation, a sighting element, a sight bar carrying said element and mounted for universal movement, sight operating means comprising a member mounted for rotation about two axes perpendicular to each other and for translation in the direction of one of said axes, means operated in response to a movement of the gun in azimuth for imparting an equal and opposite angular movement to said member about the last-mentioned axis, said sight bar being pivotally connected to said member eccentrically with respect to the said last-mentioned axis whereby a lead in azimuth of the gun relatively to the line of sight is established, means operated in response to a movement of the gun in elevation for swinging said member about the other axis an equal amount in the opposite direction, and means for adjusting said member in translation in accordance with the vertical component of the targets velocity whereby a lead of the gun in elevation is established.

3. In a gun sight for use with and mounted on a gun mounted to swing in azimuth and elevation, a sighting element, a sight bar mounted for universal movement, said sighting element being xed to said bar, a yoke having a slideway, a support in which said yoke is mounted for rotation into parallelism with the targets course, means operated in response to a movement of the gun in azimuth for imparting an equal and opposite angular movement to said yoke, a member pivotally connected to said sight bar and mounted for adjustment along said slideway in accordance with the horizontal speed of the target to establish a horizontal lead component of the gun relatively to the line of sight, means operated in response to a movement of the gun in elevation for swinging said support about a horizontal axis whereby the axis of rotation of said yoke is constantly maintained in a vertical position, and operator-controlled means for adjusting said support vertically in accordance with the vertical component of the targets velocity whereby said sight bar is moved relatively to the gun to establish a vertical lead component.

RICHARD M. ELLIOTT.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number I Name Date 1,968,127 Clementi July 31, 1934 FOREIGN PATENTS Number Country Date 186,099 Great Britain Sept. 18, 1922 le Kw 

